The inventive concepts described herein relate to an image sensor.
An image sensor is a semiconductor device that converts an optical image into an electrical signal. An image sensor reads image information by converting charge generated in a pixel responsive to light into a voltage signal. Image sensors can be generally classified as charge-coupled device (CCD) image sensors or complementary metal oxide semiconductor (CMOS) image sensors.
With recent developments in computer and communication industries, CMOS image sensors are becoming widely used in various electronic devices such as digital cameras, camcorders, game consoles, security cameras, medical micro-cameras, robots and the like. As the integration density of CMOS image sensors has increased and the size of CMOS image sensors has decreased, the size of pixels (which are read units of image information) has gradually decreased.
Each of the unit pixels of a CMOS image sensor includes a photoelectric conversion unit and a charge transfer unit. The charge transfer unit transmits charge generated at the photoelectric conversion unit from incident light to a charge detection unit. CMOS image sensors typically include an active pixel area and an optical black area. The active pixel area is an area that receives incident light and converts the incident light into an electrical signal. The optical black area is an area that blocks transmission of light so as to provide the basis for a black signal of the active pixel area.